WO2009/050831A1 discloses a distance measuring apparatus in which for measuring a distance to a target, electromagnetic wave (for example, micro wave) signal is transmitted to the target, the signal reflected by the target is received, a time period during which the signal travels to the target and then back to the apparatus is measured, a change in phase (a phase difference) of the signal is detected, a rough distance measurement is carried out based on the time period, a precise distance measurement is carried out based on the phase difference, and the rough distance measurement and the precise distance measurement are combined to obtain a final measurement value of distance. According to the distance measuring apparatus described above, distance measurement can be carried out with a relatively high accuracy for a wide range, because the rough distance measurement using time and the precise distance measurement using phase difference are combined.
However, in the apparatus described above, accuracy of the precise distance measurement using phase difference is restricted by accuracy of the rough distance measurement using time.
Accordingly, there is a need for a distance measuring apparatus and a distance measuring method which are not restricted by accuracy of the rough distance measurement using time.